1. Field of the Invention
This invention relates to methods and devices used for electrically connecting medical glucose monitors to glucose sensor electrodes as well as for testing the operation of the glucose monitors, monitor cables and glucose sensors.
2. Description of the Related Art
Over the years, a variety of implantable electrochemical sensors have been developed for detecting or quantifying specific agents or compositions in a patient""s blood. For instance, glucose sensors are being developed for use in obtaining an indication of blood glucose levels in a diabetic patient. Such readings are useful in monitoring or adjusting a treatment regimen which typically includes the regular administration of insulin to the patient. Thus, blood glucose readings can improve medical therapies with semi-automated medication infusion pumps of the external type, as generally described in U.S. Pat. Nos. 4,562,751; 4,678,408; and 4,685,903; or automated implantable medication infusion pumps, as generally described in U.S. Pat. No. 4,573,994, which are incorporated herein by reference.
Generally, small and flexible electrochemical sensors can be used to obtain periodic readings over an extended period of time. In one form, flexible subcutaneous sensors are constructed in accordance with thin film mask techniques in which an elongated sensor includes thin film conductive elements encased between flexible insulative layers of polyimide sheets or similar material. Such thin film sensors typically include a plurality of exposed electrodes at one end for subcutaneous placement with a user""s interstitial fluid, blood, or the like, and a corresponding exposed plurality of conductive contacts at another end for convenient external electrical connection with a suitable monitoring device through a wire or cable. Typical thin film sensors are described in commonly assigned U.S. Pat. Nos. 5,390,671; 5,391,250; 5,482,473; and 5,586,553 which are incorporated herein by reference.
Thin film sensors generate very small electrical signals which can be read by external glucose monitors. These monitors can be portable, and can be attached to the patient, such as for example, on a belt clip. Applicant""s clinical studies have shown that an electrical cable may be provided for the transmission of these small signals from the sensors to the glucose monitor. But given the environment in which these cables are used, special characteristics can be useful.
Thus a glucose monitoring system includes connectors between the cables, leads, electrodes and monitors such as those described in pending U.S. patent application Ser. No. 09/346,835, filed Jul. 2, 1999 and entitled xe2x80x9cInsert Set for a Transcultaneous Sensorxe2x80x9d and U.S. patent application Ser. No. 09/377,472, filed Aug. 19, 1999 and entitled xe2x80x9cTelemetered Characteristic Monitor System and Method of Using Same, both of which are incorporated herein by reference. Although a well designed system will have minimal operational problems, it is possible that a problem might arise with the integrity of the cables, sensor electrodes or monitor during their use. The system connectors or the cables may become loose or bent, resulting in a poor or open circuit. The sensor electrodes could degrade. The glucose monitor could become inoperative due to any number of causes. Thus, it is desirable to provide a system that is simple to use so that a patient can easily identify any operational problems with the system.
A glucose monitoring system test plug as well as an electric cable for electrically connecting a glucose monitor to a glucose sensor set are provided. In one embodiment, the electric cable comprises a cable member, a first connector and a second connector. The cable member in turn comprises at least one insulated conductor, a conductive shielding layer disposed around the at least one insulated conductor; and an insulating layer disposed around the conductive shielding layer.
In one aspect, the first connector comprises a housing having a first bore which is adapted to receive a sensor set cable fitting and a first conductive contact disposed within the first bore. The first conductive contact is electrically coupled to the insulated conductor and is adapted to be removably electrically coupled to a sensor set conductive contact. In one embodiment of the present invention, a key fitting is formed within the first bore and is adapted to mate with the glucose sensor set in one orientation. There is further provided a releasable coupler disposed on the housing which is adapted to releasably couple the housing with the glucose sensor set.
In another aspect, the second connector comprises a housing having a second bore. The second connector is adapted to releasably couple the second connector with the glucose monitor. There is a second conductive contact disposed within the second bore which is electrically coupled to the insulated conductor. The second conductive contact also is adapted to be removably electrically coupled to a glucose monitor conductive contact.
In yet another aspect, the glucose monitoring system test plug is for use with a glucose monitor cable which is adapted to electrically couple to a glucose monitor. The test plug comprises a housing and a fitting affixed to the housing. The fitting is adapted to electrically couple the test plug to the glucose monitor cable. The test plug further comprises an electrical circuit which is adapted to provide a known test signal to the cable and the glucose monitor in order to test the operational performance of the glucose monitor and the glucose monitor cable when the test plug is coupled to the glucose monitor cable and when the glucose monitor cable is coupled to the glucose monitor.
In an alternative embodiment, the test plug is provided for use with a glucose monitor. The test plug comprises a housing and a fitting affixed to the housing. The fitting is adapted to electrically couple the test plug to the glucose monitor. The test plug further comprises an electrical circuit which is adapted to provide a test signal to the glucose monitor to test the operational performance of the glucose monitor when the test plug is coupled to the glucose monitor.
In yet another embodiment, the test plug can alternatively provide a releasable electrical connection with either the electrical cable or the glucose monitor.